This invention relates to a solid-state or semiconductor photoelectric converter. The photoelectric converter may be a photodiode, a line sensor, or an image pickup device.
A solid-state image pickup device is generally of the charge transfer type as named in the art, and is developed either according to a frame transfer scheme or an interline transfer scheme. As will later be described in detail with reference to more than a dozen figures of the accompanying drawing, an image pickup device of the type described, has a principal surface and includes a two-dimensional array of photosensitive semiconductor regions contiguous to the principal surface in rows and columns for converting an optical image projected onto the principal suface to a pattern of electrical signals. The principal surface, as herein called, of the image pickup device will become clear as the description proceeds. The image pickup device further includes reading devices for the respective columns of photosensitive semiconductor regions along the principal surface for reading the electrical signals, and a semiconductor substrate contiguous to the photosensitive semiconductor regions and the reading devices in juxtaposition with the principal surface.
Generally, the photosensitive semiconductor regions are given a conductivity type of the semiconductor substrate and a higher impurity concentration. In this context, the semiconductor substrate, as herein named, is a bulk of a semiconductor wafer that does not comprise the photosensitive semiconductor regions and the reading devices.
Such image pickup devices are compact, light in weight, low in power consumption, and highly reliable like other solid-state devices and are in rapid progress. An image pickup device of the charge transfer type is additionally advantageous as regards noise, afterimages or residual images, scorching, and others, as compared with an image pickup or camera tube now in use. The image pickup device has, however, had serious problems of blooming and smear phenomena. The smear phenomenon is a sort of crosstalk among electrical signals of the pattern.
A line sensor comprises only one of the columns of photosensitive semiconductor regions and a reading device therefor. The column may be called a row depending on the circumstances. The photosensitive semiconductor regions in such a row are responsive to a linear optical image and are for producing a linearly distributed electrical signals. It is possible to understand that the array of photosensitive semiconductor regions of a solid-state image pickup device comprises such an elementary row of photosensitive semiconductor regions and additional rows. The line sensor has the problems of blooming and smear phenomena.
A photodiode may comprise only one photosensitive semiconductor region and need not comprise a reading device therefor. The photosensitive semiconductor region will be called a unit photosensitive semiconductor region and is responsive to a picture element of the optical image. An elementary electrical signal produced by the unit photosensitive semiconductor region is related to a quantity of light at the picture element. It is possible to understand that each row of photosensitive semiconductor regions described hereinabove, comprises such a unit photosensitive semiconductor region and additional photosensitive semiconductor regions. The photodiode has the problem of blooming. A photodiode comprising a plurality of individual photosensitive semiconductor regions additionally has the problem of smear phenomenon.